"Of course we can win..."
That is what the Democrats are afraid of. Much of the leadership of the Democratic Party today comes out of the anti-VietNam war protestors. Their article of faith is that the US could not win a guerilla war (and should not be able to). If the US can win in Iraq, then maybe it could have won in VietNam. If the US could have won in VietNam, then our leaving was not prudence, but cowardice, defeatism and a betrayal of our allies and the men who had served prior to our withdrawal. They can never admitt that, not to the country, not to the veterans of 'Nam, not even to themselves. So, to them, the War in Iraq is unwinable and therefore we are losing. QED.